Method for determining normal measurements for a patient

ABSTRACT

Method and system for determining a norm to apply to a patient being examined in which at least one physical characteristic of the patient is determined from the examination and guidelines relating thereto are obtained. Information about the patient other than from the examination and established norms for each characteristic are also obtained. An established norm to be applied to the patient is selected based on the determination of the characteristic(s), the guidelines relating to the determination thereof, and the information about the patient other than from the examination. The selection of the norm is performed by an inference engine. The norm is applied to the characteristic, e.g., a measured anatomical feature, to obtain a normal value therefor. The measured anatomical feature is compared to the normal value to determine whether it is indicative of a normal or abnormal condition.

The present invention relates generally to a method and system fordetermining a normal value or range of normal values of a physicalcharacteristic of a patient and more specifically to a method and systemfor determining a norm to be used for assessing normalcy of ananatomical feature.

It is important to know whether fetuses are growing normally for thepurpose of detecting potential abnormal growth conditions, such asintrauterine growth retardation, in order to enable treatment of suchconditions, when possible. When determining whether a fetus is growingnormally, current medical modalities are used to obtain physicalmeasurements of the fetus. Values relating to the fetus's growth arederived from the measurements using known formula and a determination isthen made whether the derived values fall within a range of valuescorresponding to those of a normal condition for the fetus, i.e., afetus undergoing normal growth.

The range of values corresponding to a normal condition varies for eachfetus because they depend on numerous criteria. For example, somecriteria include the geographic region in which the mother lives, theethnic background of the mother and the mother and fetus's healthhistory.

To date, there is no easy way to obtain the range of values for everyindividual. Typically though, norms are used. Norms are an acceptedmetric or criteria for a specific clinical evaluation, one example beinga growth chart. Typically, norms are stored in medical modalities usedin patient examination, such as in ultrasound imaging equipment. Normsusually take the form of a table or a formula.

There are numerous norms which correlate measurements of a physicalcharacteristic of a fetus to the gestational age for the purpose ofdetermining whether the fetus is growing at a normal rate. Themeasurements correlated to gestational age may be any measurableparameter relating to the physiology of the fetus, such as the length orsize of a particular bone, the diameter of a particular bone, the sizeof a particular organ, the circumference of a part of the fetus (head orabdomen) and other similar characteristics or ratios of two or more ofthe measurements. These measurements are usually obtained during anultrasound procedure but may be obtained in other ways known to thoseskilled in the art.

Once a measurement of a particular bone or organ or part of the fetus isobtained, reference is made to a norm, i.e., a table or formula, toobtain a gestational age corresponding to that measurement In otherwords, the norm expresses what the age of a fetus undergoing normalgrowth should be when it has that measurement. Each table or formulaalso typically includes an error or standard deviation to thereby definerange of the gestational age. If the gestational age of the fetus, asdetermined from an assumed date of conception, is outside of thegestational age range obtained from the table or formula, then thiswould be indicative of abnormal growth. On the other hand, when thegestational age of the fetus as determined from the assumed date ofconception falls within the gestational age range obtained from thetable or formula, then normal growth is indicated.

FIG. 1 shows an example of a table relating several characteristics of afetus to gestational age, namely, the circumference of the head(designated HC), the circumference of the abdomen (designated AC) andthe length of the femur (designated FL). The data in this table isderived by Hansmann, Hackeloer, Staudach and Wittman and is set forth in“Ultrasound Diagnosis in Obstetrics and Gynecology”, Springer-Verlag,New York 1986. The table provides an expectation of the gestational agefor measurements of the head circumference, abdomen circumference andfemur length within measurement ranges, e.g., a measurement range of thelength of the femur is from 1.0 cm to 7.5 cm. Thus, in use for example,if the femur length of a fetus is measured as 3.1 cm, the expectedgestational age would be 20 weeks. If the age of the fetus based on theassumed date of conception is for example 30 weeks, this would likely bean indication of abnormal growth.

Instead of a table, a formula can be used to obtain an expectedgestational age range. One formula derived by Hadlock, Deter, Harristand Park and set forth in “Estimating Fetal Age: Computer AssistedAnalysis of Multiple Fetal Growth Parameters”, Radiology 1984, 152:497-501, is:10.35+(2.460*FL)+(0.170*(FL ²))=Gestational Age (weeks)

wherein FL is measured femur length expressed in cm. This formula isapplicable for a range of femur length from 0.64 cm to 8.0 cm. Thestandard deviation, which provides a range of the gestational age,varies from 1.38 weeks to 3.12 weeks as follows: Standard Lower limit(weeks) Higher limit (weeks) deviation 12 18 1.38 18 24 1.80 24 30 2.0830 36 2.96 36 42 3.12

Another formula derived by Hohler and Quetel and set forth in “FetalFemur Length: Equations for Computer Calculation of Gestational Age fromUltrasound Measurements”, American Journal of Obstetrics and Gynecology,Vol. 143, No. 4, Jun. 15, 1982, pp.479-481 is:9.18+2.67*FL+0.16*(FL ²)=Gestational Age (weeks)wherein FL is measured femur length expressed in cm. This formula isapplicable for a range of femur length from 1.0 cm to 8.0 cm.

In a similar manner, tables and formulas are derived for othermeasurable physical characteristics, such as abdominal circumference(AC), biaparietal diameter (BPD), head circumference (HC),occipital-frontal diameter (OPD) and others as set forth in DICOM(Digital Imaging and Communications in Medicine) Supplement 26.

A problem arises in that each table or formula is likely to provide adifferent range of expected gestational age so that when one table orformula is used, the measured physical characteristic might be indicatedas normal growth but if another table or formula were to be used, thesame measured physical characteristic would be indicative of abnormalgrowth.

Although gestational age is used above as an indicator of normal orabnormal growth. Estimated fetal weight (EFW) can also be used. Thereare norms which correlate a measured physical condition, such as thelength of a bone or circumference of the head or abdomen, to estimatedfetal weight. In this case, if the estimated fetal weight determinedfrom the assumed date of conception (obtained from a table for example)deviates from the estimated fetal weight derived from the norm, thenthis would be indicative of an abnormal condition.

It is also important to know whether organs and bones are in a normalproportion to the rest of the body and growing at a normal rate becauseproblems may arise if a particular organ is not in the proper proportionwith the rest of the body. For example, the heart and the heart valvesusually grow commensurate with age and if a heart valve is not growingat the proper rate or is otherwise not in proportion to the rest of thebody, it may be indicative of cardiological problems.

Accordingly, it is an object of the present invention to provide amethod and system for determining a range of normal measurements of aphysical characteristic of a patient. Herein, a “patient” is used torefer to an object or organism that grows such as a fetus as well aschildren and adults. A “physical characteristic” may be any property(length, diameter, etc.) of an anatomical feature (bone, organ, etc.).

It is another object of the present invention to provide a method for“patient centered” care, i.e., determining the particular needs ofindividual patients and then tailoring care to them.

It is another object of the present invention to provide a method andsystem for determining whether measurements of a fetus are within arange of normal measurements individually selected for that patient.

It is another object of the present invention to provide a method andsystem for determining whether measurements of an anatomical featurewithin a range of normal measurements individually selected for thatpatient.

In order to achieve these objects and others, a method for determining anorm to apply to a patient in accordance with the invention comprisesexamining the patient, determining or measuring at least one physicalcharacteristic of the patient from the examination, obtaining guidelinesrelating to the determination or measurement of each characteristic fromthe examination, obtaining information about the patient other than fromthe examination, obtaining established norms for each characteristic andselecting one of the established norms to be applied to the patientbased on the determination or measurement of the characteristic, theguidelines relating to the determination thereof, and the informationabout the patient other than from the examination. The selection of thenorm, i.e., the determination of the most appropriate norm for thepatient, may be performed by an inference engine.

If the patient is a fetus and the norm is one which provides as outputan expected gestational age or age range upon input of the physicalcharacteristic, then the characteristic as determined from theexamination is input into the norm to obtain the expected gestationalage or age range. The age of the fetus (as determined for example basedon the assumed date of conception) is then compared to the expected ageor age range to see whether it is proximate the expected age or withinthe expected range (and thus indicative of a normal growth condition).Otherwise, if the age of the fetus determined from the assumed date ofconception is relatively distant from the expected age or outside of theexpected age range, e.g., higher, then this would be indicative ofabnormal growth.

Depending on the norm, the norm might be applicable to a physicalcharacteristic which is derived from a plurality of measured anatomicalfeatures, e.g., a ratio of two anatomical features (such as a ratio ofthe head circumference to abdomen circumference (HC/AC) or femur lengthto abdomen circumference (FL/AC)). In this case, a normal value or arange of normal values for the physical characteristic, i.e., the ratio,is obtained and compared to a ratio derived from the measured anatomicalfeature of the fetus to determine whether the ratio of anatomicalfeatures is indicative of a normal or abnormal condition.

The examination may be performed using any medical modality such as anultrasound imaging system, an MRI (magnetic resonance imaging) system, aCT system and other imaging modalities. The anatomical feature may be alength, size or diameter of a bone in the patient or a circumference ofa head or abdomen.

In another embodiment, a norm for use for a patient is determined byexamining the patient, determining or measuring at least one physicalcharacteristic of the patient from the examination and expressing it inXML syntax. Further, guidelines relating to the determination of thecharacteristic are obtained and described using a methods ontology basedon semantic web technology. Information about the patient other thanfrom the examination is obtained from a hospital or departmentalinformation system using HL7 messaging which uses XML syntax.Established norms for each characteristic, e.g., an anatomical featureor a ratio of two anatomical features, are obtained such as from one ormore libraries thereof or from memory in the medical modality, andexpressed in XML syntax. Thereafter, an inference engine is provided toreceive the determination or measurements of each characteristic and theguidelines relating thereto and the information about the patient otherthan from the examination and selects one of the established norms to beapplied to the patient based thereon.

A system for determining a norm to be used for a patient in accordancewith the invention comprises a modality for obtaining measurements of aphysical condition of a patient and enabling characteristics relating tothe physical characteristics of the patient to be derived, a processorcoupled to the modality, a repository of medical information about thepatient coupled to the processor, at least one library of norms relatingto the physical characteristics of the patient coupled to the processor,and at least one library coupled to the processor and containingclinical guidelines associated with a procedure used by the modality toderive the measurements. The processor receives the derivedcharacteristics of the patient from the modality, the measurements fromthe modality, medical information about the patient from the repositoryof medical information, the norms from each library of norms and theclinical guidelines from each library of clinical guidelines and selectsone of the norms which is most appropriate for use with the patient.Data on the selected norm is provided, including the upper and lowerlimits on the range of the input parameter and various details about theorigins of the norm. By applying the norm to the measurements of thepatient from the modality, the normalcy or abnormalcy of the patient canbe deduced.

In one embodiment, the links between the processor, the hospital ordepartmental information system, each library of norms and each libraryof clinical guidelines are Internet or Intranet connections.

To facilitate easy communications, the modality is arranged to expressthe measurements of the patient and the derived values relating tophysical characteristics of the patient in XML syntax, and therepository of medical information about the patient is arranged toremotely communicate with the processor using HL7 messaging using XMLsyntax. Also, each library of norms is arranged to express the norms inXML syntax and each library of guidelines is arranged to describe theguidelines using a methods ontology based on semantic web technology.

The invention, together with further objects and advantages hereof, maybest be understood by reference to the following description taken inconjunction with the accompanying drawings, wherein like referencenumerals identify like elements and wherein:

FIG. 1 is a table showing derived correlations between anatomicalfeatures and gestational age.

FIG. 2 is a flowchart showing the method in accordance with theinvention.

FIGS. 3A and 3B are schematic flowcharts showing the manner in which thepresent invention functions.

Referring initially to FIG. 2, a method in which a recommendation on thenormalcy of one or more physical characteristics of a fetus isdescribed.

One or more physical measurements of the fetus are obtained during anexamination of the mother at Step 10. This may entail measuringanatomical features of the fetus, for example, using an ultrasoundsystem during a scanning procedure with the measurements beingdetermined during the scanning or with the measurements being determinedoff-line at a workstation. The measurements of the fetus may include thefemur length (FL), head circumference (HC), abdomen circumference (AC)and biaparietal diameter (BPD) as well as other anatomical features aslisted in DICOM Supplement 26. For further processing and use in theinvention, the measurements are preferably expressed in XML (extensiblemark-up language) format.

Physical characteristics are derived from the measurements at Step 12. Aphysical characteristic may either be the measurement itself or a valuederived from one or more measurements, such as a ratio of twomeasurements. The measurement or value is selected based on availablenorms, i.e., it must be one for which a norm is known.

Information about the fetus, other than the measurements of the physicalcharacteristics obtained during the examination, is also obtained atStep 14 from one or more hospital information systems, and possiblydepartmental information systems. The hospital information system may bequeried to provide the information by a query containing the patient'sidentification and the requested information. The requested informationmay include the fetus's or mother's age, weight, gender and ethnicity.

To communicate with the hospital information system, the system whichdetermines which norm to apply is resident on a processor (as describedbelow with reference to FIGS. 3A and 3B) and uses a form of messagingconducive to information exchange such as HL7 messaging. This type ofmessaging also preferably uses XML syntax for further processing of theinformation from the hospital information system. A vocabulary isprovided, either from the hospital information system or on theprocessor, and used to indicate and define any coded terms in theinformation provided by the hospital information system. Informationabout the mother can also be provided, such as information about theuterus and the presence of other fetuses.

Clinical guidelines associated with the procedure used to derive thephysical characteristics are retrieved from one or more libraries ofsuch clinical guidelines at Step 16 and preferably described using amethods ontology based on semantic web technology. An ontology(knowledge base) is a conceptualization of a domain of guidelines. Oneskilled in the art would understand the manner in which a methodsontology based on semantic web technology is configured and used.

The clinical guidelines provide the steps associated with the procedureand highlight the measurements required and any additionalsteps/measurements to be taken to verify if a ratio is abnormal.

Established norms are retrieved at Step 18 from one or more libraries ofnorms and preferably expressed in XML syntax. The norms may be residenton software or hardware of the medical apparatus used during theexamination of the fetus, or may be accessed through an Internet orIntranet connection by the processor.

The measurements obtained during the examination of the fetus, theclinical guidelines used to derive the physical characteristics, theinformation about the fetus (and optionally mother) and the establishednorms are input to an inference engine resident on the processor at Step20. The inference engine derives a norms recommendation based on theinput data, i.e., the most appropriate norm for use with the input data.The norms recommendation is a selected norm, i.e., either a table orformula, to which the physical characteristic obtained or derived fromthe examination will be applied to obtain an indication of normalcy ofthe physical characteristic with respect to gestational age.

For example, the selected norm may be the formula derived by Hadlock etal. set forth above (10.35+(2.460*FL)+(0.170*(FL²))=Gestational Age(weeks) wherein FL is measured femur length expressed in cm). The normwould also have associated limits of the range of input values, i.e., arange of permitted input measurements, in this case from 0.64 cm to 8.0cm) and would include its origin. The origin would specify the codevalue of the DCMR or local coded concept, the coding scheme designatorof the DCMR or local coded concept and the code meaning of the DCMR orlocal coded concept.

The measurement is then input to the selected norm to provide theexpected gestational age or age range (Step 22).

A standard deviation or error is determined, if any is associated withthe norm, in order to provide a range of the gestational age (Step 24).That is, if the femur length was measured as 2.0 cm, the gestational ageprovided by the formula would be 15.95 weeks with the deviation of 1.38weeks so the gestational age range would be 14.57 weeks to 17.33 weeks.

The age of the fetus obtained from the assumed date of conception wouldbe compared to this range for the purpose of assessing growth normalcyor abnormalcy (Step 26). Thus, if the age from the assumed date ofconception is 25 weeks, it would be outside of the range of normalgrowth and thus indicative of abnormal growth.

In the event an abnormal condition is determined, then a determinationis made whether the determination of the abnormal condition is the firstdetermination or a subsequent confirmation of the first determination(Step 28). If it is the first determination of an abnormal condition,then a feedback loop to the input or obtaining of the physicalmeasurements (Step 10) may be used to confirm the abnormal condition.That is, by providing a feedback and requiring the re-entry orre-obtaining of the physical measurements, errors in data entry ormeasurement errors can be reduced. Also, additional measurements may beobtained after an abnormal condition is initially determined to aid inthe confirmation of the abnormal condition in a subsequent analysis ofthe physical measurements. Once the abnormal condition is confirmed,then the diagnosis results in an abnormal condition.

Typically, the selected norm includes not only the value of the 50^(th)percentile but can and should also include information that describesthe distribution width, e.g., the standard deviation. Clinically,physicians want to know if the biometric value is outside some range asthe 10/90 (below the 10^(th) percentile or above the 90^(th) percentile)or 5/95 or 2 STD (standard deviations 3/97) range.

Referring now to FIGS. 3A and 3B, the components used in the method inaccordance with the invention are set forth in a flow chart. Themodality 30, e.g., an ultrasound machine, is present in an examinationroom and the results of the examination are obtained and analyzed toderive one or more measurements of anatomical features of the fetus byan ultrasound technician operating the ultrasound machine. Themeasurements or values derived from the measurements are preferablyexpressed in XML syntax.

The measurements are provided to a processor 32 which may be integralwith or remote from the ultrasound machine.

The processor 32 is also coupled to a hospital information system (HIS)34 or other repository of medical information about the fetus andoptionally the mother. The hospital information system 34 provides dataabout the fetus and mother upon request by the processor 32. Thespecific type of information to be obtained from the hospitalinformation system 34, e.g., age, weight, ethnicity, gender, isdetermined by the processor 32.

Instead of general hospital information, departmental informationsystems can be used to provide more specific information, for example, aradiology information system (RIS) which would provided radiologicalinformation, a cardiological information system (CIS) which wouldprovide cardiological information, etc.

The processor 32 is also coupled to one or more libraries of norms 36which contain data about each norm including for example, when the normis an equation, the author, the application, the file type, the source,the input parameter and range, the output parameter and unit and anequation for determining the output parameter from the input parameter.Each norm can be modeled to include four aspects, a target concept whichis the concept to be computed using the norm, a list of dependencieswhich is a list of concepts on which the computation of the targetconcept depends, an equation which is a function that provides thetarget concept based on the dependency and one or more applicabilityconstraints. With respect to the applicability constraints, some normsare applicable in certain contexts and not others. These constraints arethe criteria which determine whether one norm is better than another.

A norm can also be a table listing different values of the physicalmeasurement and an output parameter and unit for each different value.The table would also include the author, the file type, the source andany applicability constraints. The table could also include a standarddeviation.

The processor 32 is also coupled to one or more libraries 38 containingclinical guidelines associated with the procedure that obtained themeasurements or the derivation of the physical characteristics.

The hospital information system 34, the libraries of norms 36 and thelibraries of clinical guidelines 38 may be operated independently of oneanother, each as a stand alone system. Each of them is however linked tothe processor.

Once the processor 32 receives all of the inputs, it derives a normrecommendation, i.e., selects one of the norms from the library 34 basedon the input data. This norm would be used to analyze the physicalcharacteristics obtained or derived from the examination. The processor32 displays the norm recommendation with any or all of its associatedinformation, e.g., its derivation, origins, author, limitations. Thenorm recommendation may be entered into a report or workstation at whichtime, the measured anatomical feature of the patient, or a derivedvalue/ratio based on one or more measured anatomical features would beentered into the norm for the purpose of assessing whether the physicalcharacteristic of the patient (the measured anatomical feature or ratioof anatomical features) is proximate the output of the norm or within arange provided by the norm. If so, the patient would be diagnosed withnormal growth. On the other hand, a determined physical characteristicdistant from the output of the norm or outside of the range provided bythe norm could be considered abnormal growth.

As shown in FIG. 3A, the processor 32 is resident in the modality 30 orotherwise arranged in connection therewith. In this case, the modality30 would be constructed to provide the functions of the processor 32,i.e., include appropriate communications software and hardware to enableconnections to the hospital information system 34, the libraries ofnorms 36 and the libraries of clinical guidelines 38 to be established.

In the alternative, the modality 30 could be constructed independent ofthe processor 32 which performs the functions in accordance with theinvention and thus the processor 32 could be implemented as a servicefor independently operating modalities. Thus, as shown in FIG. 3B, thelinks between the processor 32 and the hospital information system 34,the libraries of norms 36 and the libraries of clinical guidelines 38may be connections over the Internet or Intranet connections. Theprocessor 32 could also be wired directly to the hospital informationsystem 34, the libraries of norms 36 and the libraries of clinicalguidelines 38. In these embodiments, the processor 32 would beindependent of the modality 30.

Although reference is made above to determining a norm of a physicalcharacteristic of a fetus, the method and system in accordance with theinvention are applicable to any growing objects having quantifiablegrowth charts or curves including people, children in particular, aswell as an organ or bone which is expected to grow in proportion to therest of the body.

That is, the present invention is applicable is determining whetherorgans and bones of children and adults are in normal proportions. Forexample, in accordance with the invention, it is possible to determinewhether heart valves are at a normal size in order to detect myocardialinfractions which might arise if the heart valves were not in a properproportion. In this case, the size of the heart valves are measured,e.g., using ultrasound, and additional information about the patient isobtained in the manner described above. Clinical guidelines about theheart valve measurement procedure are also obtained. This information isprocessed to obtain a value or range of values indicative of a heartvalve at a normal size for the individual. Standard deviations couldalso be obtained. The measured size of the heart valve would be comparedto the obtained value or range of values to assess whether the heartvalve is a normal size or not. In the same manner, the invention can beused to determine the normalcy of bones and other organs (i.e., whetherthey are in a normal proportion) as well as the normal or abnormalgrowth of organs and bones.

Although illustrative embodiments of the present invention have beendescribed herein with reference to the accompanying drawings, it is tobe understood that the invention is not limited to these preciseembodiments, and that various other changes and modifications may beeffected therein by one of ordinary skill in the art without departingfrom the scope or spirit of the invention.

1. A method for determining a norm for use in assessing normalcy of apatient being examined, comprising the steps of: determining at leastone physical characteristic of the patient from the examination;obtaining guidelines relating to the determination of the at least onecharacteristic from the examination; obtaining information about thepatient other than from the examination; obtaining established norms forthe at least one characteristic; and selecting one of the establishednorms to be applied to the patient based on the determination of the atleast one characteristic, the guidelines relating to the determinationof the at least one characteristic and the information about the patientother than from the examination.
 2. The method of claim 1, wherein theat least one characteristic is an anatomical feature, further comprisingapplying the norm to the anatomical feature to obtain a normal value fora measurable anatomical feature or a range of normal values for ameasurable anatomical feature and comparing the determined anatomicalfeature of the patient to the normal value or range of normal values todetermine whether the determined anatomical feature is indicative ofnormalcy of the patient or abnormalcy of the patient.
 3. The method ofclaim 1, wherein the at least one characteristic is a ratio of twoanatomical features, further comprising applying the norm to the ratioto obtain a normal value for the ratio or a range of normal values forthe ratio and comparing a ratio derived from the determined anatomicalfeatures of the patient to the derived normal value or range or range ofnormal values to determine whether the at least one anatomical featurefalls is indicative of normalcy of the patient or abnormalcy of thepatient.
 4. The method of claim 1, wherein the step of performing theexamination comprises the step of performing an ultrasound examinationof the patient.
 5. The method of claim 4, wherein the step ofdetermining the at least one characteristic comprises the step ofmeasuring a length, size or diameter of a bone in the patient ormeasuring a circumference of a head or abdomen.
 6. The method of claim4, wherein the step of determining the at least one characteristiccomprises the steps of measuring at least two anatomical features andcalculating a ratio of two anatomical features, guidelines relating tothe ratio of the two anatomical features being obtained.
 7. The methodof claim 1, further comprising expressing the determination of the atleast one characteristic in XML syntax.
 8. The method of claim 1,further comprising expressing the established normal ranges of the atleast one characteristic in XML syntax.
 9. The method of claim 1,wherein the information about the patient other than obtained from theresults of the examination is obtained from a hospital or departmentalinformation system using HL7 messaging which uses XML syntax.
 10. Themethod of claim 9, wherein the information about the patient is coded inthe hospital or departmental information system, further comprisingaccessing a vocabulary to decode the information about the patient priorto the selection of one of the established norms.
 11. The method ofclaim 1, wherein the selection of one of the established norms isperformed by an inference engine.
 12. A method for determining a normfor use in assessing normalcy of a patient being examined, comprisingthe steps of: determining at least one physical characteristic of thepatient from the examination; expressing the determination of the atleast one characteristic in XML syntax; obtaining guidelines relating tothe determination of the at least one characteristic from theexamination, the guidelines being described using a methods ontologybased on semantic web technology; obtaining information about thepatient other than from the examination from a hospital or departmentalinformation system using HL7 messaging which uses XML syntax; obtainingestablished norms for the at least one characteristic; expressing theestablished normal ranges of the at least one characteristic in XMLsyntax; and providing an inference engine to receive the determinationof the at least one characteristic, the guidelines relating to thedetermination of the at least one characteristic and the informationabout the patient other than from the examination and selecting one ofthe established norms to be applied to the patient based thereon.
 13. Asystem for determining a norm for use in assessing normalcy of apatient, comprising: a modality for obtaining physical measurements of apatient and enabling at least physical characteristic of the patient tobe derived; a processor coupled to said modality; a repository ofmedical information about the patient coupled to said processor, atleast one library of norms relating to characteristics of the patientcoupled to said processor; and at least one library coupled to saidprocessor and containing clinical guidelines associated with a procedureused by said modality to derive the characteristics; said processorbeing arranged to receive the characteristics of the patient derived bysaid modality, medical information about the patient from saidrepository of medical information, the norms from said at least onelibrary of norms and the clinical guidelines from said at least onelibrary of clinical guidelines and select one of said norms which ismost appropriate for use with the patient.
 14. The system of claim 13,wherein links between said processor, said repository of medicalinformation, said at least one library of norms and said at least onelibrary of clinical guidelines are Internet or Intranet connections. 15.The system of claim 13, wherein said modality is arranged to express themeasurements of the patient and the derived values relating to physicalconditions of the patient in XML syntax.
 16. The system of claim 13,wherein said repository of medical information about the patient isarranged to remotely communicate with said processor using HL7 messagingusing XML syntax.
 17. The system of claim 13, wherein said at least onelibrary of norms is arranged to express the norms in XML syntax.
 18. Thesystem of claim 13, wherein said at least one library of guidelines isarranged to describe the guidelines using a methods ontology based onsemantic web technology.
 19. The system of claim 13, wherein saidprocessor is arranged to apply the norm to the measurements obtained bysaid modality to provide an indication of a normal or abnormalcondition.
 20. The system of claim 13, wherein said processor isarranged in connection with said modality.